Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 84 near the shore to around 74 above 3000 feet. Southeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 64 to 69 near the shore to around 55 above 3000 feet. Light winds. Chance of rain 50 percent.

Sunday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 74 above 3000 feet. South winds up to 10 mph shifting to the west in the afternoon. Chance of rain 50 percent.

South Kaua’i

Today: Mostly sunny with scattered showers. Highs around 82. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 68. Light winds. Chance of rain 50 percent.

Sunday: Mostly sunny with scattered showers. Highs around 82. Northeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 30 percent.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 77 in the valleys to around 66 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Partly cloudy with scattered showers. Lows around 58 in the valleys to around 50 above 4000 feet. Light winds. Chance of rain 50 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 77 in the valleys to around 66 above 4000 feet. Light winds. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 77 to 83. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 58 to 67. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Sunday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 83. East winds up to 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 81. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 56 to 69. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 81. East winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate east southeasterly winds will prevail through the weekend. Showers will favor windward and southeast facing slopes at night and during the morning, and interior and leeward areas each afternoon. Winds will weaken Sunday night and Monday as a front approaches from the northwest. A few showers will be possible near the coast at night, with shower coverage expected to increase Monday afternoon as some moisture pools in advance of the front. This front will then move into the western islands Monday night and Tuesday, then gradually stall out and dissipate during the middle to latter part of next week. Some showery weather will likely accompany the front with windward slopes seeing the brunt of the rainfall. A return to more typical trade wind weather is looking more likely for next weekend, in line with what we should expect for this time of year.

Discussion

Currently at the surface, a weak trough of low pressure is located just north of the state, a cold front is positioned around 650 miles west-northwest of Kauai, and a 1029 mb high is centered around 1600 miles northeast of Honolulu. Light to moderate trade winds prevail in unsheltered areas early this morning, with land breezes present elsewhere. Infrared satellite imagery shows mostly clear to partly cloudy conditions in most areas, with a few pockets of enhanced cloud cover scattered about the islands. Radar imagery shows scattered showers affecting the Big Island, leeward coastal waters, and windward sections of Maui, with nothing more than isolated shower coverage elsewhere. Main short term focus revolves around rain chances and wind trends.
The trough north of the state will shift west today, allowing light to moderate trade winds prevail across the island chain, strongest over the eastern end of the state. The winds over the western islands will be light enough to allow for land and sea breeze development in most leeward areas however. An approaching front will then ease the trades from northwest to southeast down the island chain tonight and Sunday, with light and variable winds expected statewide Sunday night and Monday. A weakening front will push southward into the islands Monday night and Tuesday, allowing for a return of light to locally moderate northeast trades to develop. The front will stall out over the central islands and gradual dissipate during the middle to latter part of next week, with light to locally moderate northeasterly trades persisting.
As for the remaining weather details, the trailing moisture from the lingering trough will shift northwest through the weekend. This should lead to fewer showers over the eastern islands today, while coverage of daytime heating driven showers will be higher over Kauai and Oahu. Showers should fizzle out in most leeward areas by 8 or 9 pm, with a few showers continuing to affect windward and southeast facing slopes overnight. We should see even fewer showers on Sunday across Oahu and Maui County, with scattered daytime heating driven showers expected to affect Kauai and the Big Island once again.
The front moving in from the northwest should shift a higher precipitable water airmass back over the entire state Sunday night and Monday. This should bring an increase in shower coverage, with showers favoring areas near the coast Sunday night and early Monday, and interior and leeward areas Monday afternoon. The front is then forecast to move into the islands Monday night and Tuesday, then stall out somewhere over the central islands during the middle to latter part of next week. Some showery weather will likely accompany and stick with the front as it stalls out and gradually dissipates over the island chain, with windward slopes and coasts expected to see the brunt of the rainfall. A return to more typical trade wind weather is looking more likely for next weekend, in line with what we should expect for this time of year.

Aviation

Light to locally moderate east to southeast flow will continue for the next couple days. Sea breezes will prevail by day and land breezes at night in the more sheltered areas. Clouds and showers will prefer east facing slopes and coasts during the late night and morning hours. On the Big Island, expect cumulus build-ups over the island's interior in the afternoons and early evenings, then partial clearing overnight. Brief MVFR conditions are likely in passing showers. Otherwise, VFR conditions are expected statewide.

Marine

A trough just north of the state will help support moderate to locally strong east to southeast winds through the day. A Small Craft Advisory is in effect for those notoriously windier marine zones surrounding Maui County and Big Island, including the windward Maui and Big Island waters, where sustained easterlies will hold at between 20 and 25 knots. As a front approaches from the northwest early next week, winds will become light and variable Sunday and Monday before turning moderate northeast as high pressure builds in behind the passing weak front Tuesday.
A moderate size, long period northwest (310 degree) swell moving in this morning will lift surf from chest to slightly over head high along many north-facing shores through Sunday afternoon. A similar size, medium period northwest (320 degree) swell will come in late Sunday into early Monday. This reinforcing northwest swell will result in a slight boost to already elevated early week north and west-facing shore surf through Tuesday. A small, long period south (190 degree) swell that arrived this morning will bump south-facing shore surf up to around chest high this weekend. This swell will keep seasonable south surf in place through Monday. Lighter weekend trades will allow for relatively lower eastern exposure wind wave chop.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov